Reflecting frustration over allegations of UN mismanagement and corruption, the Senate on Wednesday agreed to a Republican-backed measure to reduce the cap on the US share of UN peacekeeping costs to 25% from the current 27.1%.
It rejected by 40-57 votes a Democratic amendment to keep the current cap for at least two more years.
"The negotiations at the UN regarding UN reform and the lowering of UN peacekeeping dues is under way. Let us ensure that our next ambassador to the United Nations has an opportunity to go to New York and work on this issue," said Senate majority leader Bill Frist, a Tennessee Republican.
If the measure becomes law, it will give the administration a stronger argument to persuade the United Nations to lower US dues.
The Senate Foreign Relations Committee is to hold a confirmation hearing next week on John Bolton, a long-time UN critic, to be US ambassador to the world body.
Bolton's choice as envoy and cuts
are seen as a double whammy
Senator Joseph Biden, the top Democrat on the Foreign Relations Committee, said the US was dealing the United Nations "a double whammy" by naming Bolton, who he called "the worst person we could possibly send" as ambassador, as it cuts its peacekeeping commitment.
Biden also said President George Bush did not specifically ask Congress to reduce the share, and included the 27.1% level in his budget.
The amendment was included in a two-year $34-billion bill authorising State Department and foreign aid programmes under debate in the Senate.
The House of Representatives has not yet taken up its version of the bill.